\begin{tikzpicture}
	\tkzDefPoints{0/0/O, -1.5/0/A, 1.5/0/C, 0/1.5/B}
	\tkzDrawSegments(O,A  O,B  O,C)
	\tkzMarkRightAngle(B,O,C)
	\tkzLabelPoints[right](B)
	\tkzLabelPoints[below](A, O, C)
\end{tikzpicture}

